PURPOSE: To obtain the composition, good in balance between rigidity and practical impact, excellent in mechanical characteristics and heat resistance and useful for interior automotive trim parts, etc., by blending a fibrous magnesium oxysulfate having a specific average fiber diameter and a specified aspect ratio with polypropylene resin.

CONSTITUTION: This composition is obtained by melt kneading (A) 100 pts.wt. polypropylene resin having 2-35g/10min melt flow index (at 230°C under 2.16kg load) with (B) 3-40 pts.wt. granular aggregate of fibrous magnesium oxysulfate having 0.1-2.0μm average fiber diameter and 1-50μm average fiber length and (C) 3-40 pts.wt. inorganic filler other than the component (B). Furthermore, e.g. a propylene-ethylene block copolymer is preferably used as the component (A) and, e.g. calcium carbonate or talc is preferably used as the component (C).